This invention relates to pressure control valves, and more particularly to a pressure control valve adaptable for use in a hydranttype fueling system for aircraft or for any other fluid pressure system in which it is desired to automatically regulate the pressure of fluid supplied from one part of the system to another.
It has been common, particularly in aircraft fueling systems to includes in the fluid pressure system, as at an airport, a plurality of stations at which fluid may be withdrawn, such stations located for example, at parking places where aircraft may be fueled. Each of these stations is typically connected by an underground piping system to a fluid supply tank and a pump which maintains fluid pressure in the entire system. Each of the fueling stations at an airport typically includes a hydrant and a pressure control valve bolted or otherwise semi-permanently affixed to the hydrant. A flexible hose may be coupled between the pressure control valve and the fuel tank of an aircraft. Such installations typically include the pressure control valve below the pavement surface in a pit which may be covered to prevent damage to the pressure control valve. Such installations require an individual pressure control valve for each such pit. However, since it is common to use only a portion of the fueling stations at any given time, the use of a pressure control valve permanently installed at each pit substantially increases the cost of such installations. In addition, removal of the pressure control valve for maintenance requires that the individual fueling station to which the valve is attached be shut down for a period of time while the pressure regulator valve is removed from the hydrant and repaired.
Pressure control is a particular problem in re-fueling large airplanes because of the tremendous quantities of fuel which must be supplied in a short period of time. For example, a large jet passenger plane might require 45,000 gallons of fuel to be supplied at flow rates up to 2000 gallons per minute at pressures up to 50 psig. The receiving tanks on the aircraft could be damaged by pressure beyond their design capability, so it is essential that the pressure be maintained accurately within a specified range in order to achieve the desired flow rate while avoiding any possible damage to the aircraft. Moreover, safeguards must be provided to immediately shut the flow off if the hose to the aircraft ruptures in order to prevent spilling large quantities of fuel on the ground. Such spillage at the high flow rates here involved would create a very dangerous condition.